Prosthetic leg with knee braking function

• US 20050234562A1
• Filed: 11/19/2003
• Published: 10/20/2005
• Est. Priority Date: 11/21/2002
• Status: Active Grant

• Current Assignee: Nabco Ltd. (Nabtesco Corporation)
• Original Assignee: Nabco Ltd. (Nabtesco Corporation)
• Inventors: Nakaya, Yoshiaki, Okuda, Masahiko, Imakita, Toyohiko, Fukui, Aritomo
• Granted Patent: US 7,588,604 B2
• Time in Patent Office: Days
• US Class Current: 623/44
• CPC Class Codes: A61F 2/644 of the single-bar or multi-bar linkage type
• CPC Class Codes: A61F 2/70 electrical
• CPC Class Codes: A61F 2/74 fluid , i.e. hydraulic or pneumatic
• CPC Class Codes: A61F 2/744 Vane- or curved-cylinder type actuators, e.g. actuators using rotary pistons
• CPC Class Codes: A61F 2/748 Valve systems
• CPC Class Codes: A61F 2002/6818 for braking
• CPC Class Codes: A61F 2002/6854 for locking or unlocking a joint
• CPC Class Codes: A61F 2002/7655 for measuring fluid pressure

Abstract

There is provided a prosthetic limb having a flexible knee brake function, which is designed such that it can be mechanically detected which part of the foot the load of the wearer is imposed on. In a thigh prosthetic limb (10), a joint upper member (12) including a knee plate (120) and a joint lower member (14) including a base bracket (22) integral with the frame (140) are operated to bend the knee. In the housing member (24), there are provided not only a knee axis but also a hydraulic brake circuit. There is a link mechanism (50) which allows a small relative motion between the housing member (24) and the base bracket (22) on the main body part side. The link mechanism (50) has an instantaneous center between the toe and the heel part of the prosthetic limb. This instantaneous center serves as a sensing point and detects which part of the foot the load of the wearer is imposed on by distinguishing a first case in which the wearer'"'"'s load is imposed on the heel and a second case in which the wearer'"'"'s load is imposed on the toe. Based on the detection result made by the link mechanism (50), the hydraulic brake circuit is controlled so that a flexible knee braking operation can be made.

Claims

1. A prosthetic limb comprising a joint upper member located at an upper side of a wearer'"'"'s knee and a joint lower member located at a lower side of the wearer'"'"'s knee and pivotably connected to said joint upper member such that the knee can be bent, said joint lower member including a joint component part which composes a knee joint by being connected to said joint upper member such that the knee can be bent and a main body part which is a part connected to a lower side of said joint component part and which moves only slightly compared with the bending motion of the knee with respect to said joint component part, wherein

said prosthetic limb having the following constitutional features X and Y in order to brake the bending motion of said knee flexibly,

X. a hydraulic brake circuit for producing a braking force with respect to the bending motion of the knee by flow resistance generated when a working fluid passes through said throttle, and

Y. sensing control means for detecting which part of the foot attached to said prosthetic limb the weight of the wearer is imposed on and controlling said hydraulic brake circuit in accordance with the detection signal;

and

said sensing control means has the following features y1 and y2,

y1. a link mechanism for connecting said joint component part and said main body part to each other in said joint lower member and having an instantaneous center between the toe and the heel of a foot of said prosthetic limb, and

y2. motion of a link constituting said link mechanism being detected and said hydraulic brake circuit being controlled based on the detection result.

2. A prosthetic limb according to claim 1, wherein said sensing control means comprises a sensing part for detecting which part of said foot the load of the wearer is imposed on, and a control means for controlling said hydraulic brake circuit in accordance with the detection signal coming from said sensing part.

3. A prosthetic limb according to claim 2, wherein said sensing part is of a mechanical construction.

4. A prosthetic limb according to claim 1, wherein the connection for pivotably connecting said joint upper member and said joint lower member together is a connection by means of either a single-axis using only one axis or a multi-axis using plural axes.

5. A prosthetic limb according to claim 1, wherein said hydraulic brake circuit, when controlled by said sensing control means, can be switched between a braking position for producing a braking force with respect to the bending motion of the knee and a non-braking position where the braking force is canceled.

6. A prosthetic limb according to claim 1, wherein said hydraulic brake circuit includes a first chamber into which a working fluid flows when the knee is extended, a second chamber into which a working fluid flows when the knee is bent, a passageway for intercommunicating said first and second chambers, a throttle located between said first chamber and said second chamber on said passageway and for applying a braking force to the bending motion of the knee utilizing a flow resistance of the working fluid which passes through said throttle, a check valve connected, in parallel, to said throttle on said passageway and adapted to prohibit a flow from said first chamber to said second chamber and allow a flow in the opposite direction, and a switch valve connected, in parallel, to said check valve and said throttle on said passageway and opened/closed by said sensing control means.

7. A prosthetic limb according to claim 6, wherein said switch valve is a seat valve which can be opened/closed by urging a valve body against a valve seat, and said valve body moves in a direction orthogonal to a plane of said valve seat when the valve is opened/closed.

8. A prosthetic limb according to claim 1, wherein said braking force is in such magnitude that the knee joint is slowly changed in bending angle by imposing the load of the wearer himself/herself thereon when the prosthetic limb is in a stance phase.

9. A prosthetic limb according to claim 1, wherein said sensing control means controls said hydraulic brake circuit in the following manner,

z1. when the heel of the foot of said prosthetic limb is contacted with the floor, a floor reaction force caused by grounding of the heel passes through the rear side of the instantaneous center of said link mechanism, thereby generating a rotational moment to said joint lower member in a forwardly folding direction about the instantaneous center,

z2. when the toe of the foot of said prosthetic limb is contacted with the floor, a floor reaction force caused by grounding of the toe passes through the front side of the instantaneous center of said link mechanism, thereby generating a rotational moment to said joint lower member in a backwardly folding direction about the instantaneous center, and

z3. switching is made between a braking position where a braking force is produced with respect to the bending motion of the knee and a non-braking position where the braking force is canceled, by controlling said hydraulic brake circuit depending on the direction of said rotational moment in z1 and z2.

10. A prosthetic limb according to claim 1, wherein said instantaneous center is located closer to the toe side than to the heel side of the foot.

11. A prosthetic limb according to claim 6, wherein said first and second chambers are partitioned by either a vane which is pivotable about one point or a piston which is linearly reciprocally movable.

12. A prosthetic limb according to claim 6, wherein a link for controlling said hydraulic brake circuit normally closes said switch valve under the effect of a spring.

13. A prosthetic limb according to claim 5, wherein said hydraulic brake circuit is mechanically controlled in accordance with motion of said link composing said link mechanism, and said small motion between said joint component part and said main body part is just enough to switch said hydraulic brake circuit between the braking position and the non-braking position, i.e., several mm or less in stroke.

14. A prosthetic limb according to claim 1, wherein said hydraulic brake circuit is disposed at said joint component part, and said prosthetic limb further comprises an air cylinder disposed between said joint upper member and said joint lower member and adapted to assist the bending motion and the extending motion of the knee in the swing phase.

15. A prosthetic limb according to claim 1, wherein said hydraulic brake circuit makes it possible to bend the knee joint by imposing the load of the wearer himself/herself thereon when said prosthetic limb is in the stance phase, and said prosthetic limb further comprises a hydraulic control circuit for assisting the bending motion and the extending motion of the knee in the swing phase.